Samarium acetate

Samarium Acetate Tetrahydrate (CH3C02)3Sm 4H20 13C CP/MAS chemical-shift thermometer [34]... 

The most commonly used compound for C-based solid-state temperature measurements is samarium acetate tetrahydrate. The Sm + is nine-coordinated by the oxygen atoms of three bidentate acetate ligands, two water molecules, and a bridging oxygen from an acetate ligand of an adjacent... 

Ytterbium and samarium acetates require at least 1.5 and 2.5 parts of water, respectively, for solution. 

At intermediate expansion levels, expanded droplets (balloons) have been observed by Reverchon et al. [18]. Spherical balloons were also observed by Dixon et al. [25] during the processing of polystyrene. Different nucleation structures can appear and different kinds of balloons have been observed. For example, during the precipitation of samarium acetate, empty shells of solute with a continuous surface were observed [18]. This is explained by the solute precipitation, which starts at the supercritical fluid-liquid interface and then propagates inside the liquid attracting the solute toward the separation surface. This mechanism results in the formation of hollow spherical structures [17]. 

Particle size was relatively insensitive to solute concentration in the liquid according to some authors [17,19], while others observed that backing away from saturation conditions may be abetter choice to prepare more uniform particles. A marked particle size increase and PSD enlargement with increasing concentration was observed by Reverchon et al. [18] in the SAS precipitation of yttrium, samarium, and neodimium acetates. This result is well illustrated in Figure 24.9a—c that are referred to samarium acetate precipitation from DMSO at the same pressure and temperature but at 10,40 and 65 mg/ml concentration, respectively. From these SEM images the large increase of samarium acetate particle size and PSD is evident. 

FIGURE 24.9 SEM images showing the effect of concentration on particle size, and PSD of samarium acetate nanoparticles (a) 10 g/ml DMSO (b) 40 mg/ml DMSO (c) 65 mg/ml DMSO. (Reprinted from Reverchon, E., J. Supercrit. Fluids, 15, 1-21, 1999. With permission from Elsevier.)... 

Europium acetate monohydrate (99.9 %), samarium acetate tetrahydrate (99.9 %), acetone-i 6 (D, 99.9 %) and CDCI3 (D, 99.8 %) were purchased from Wako Pure Chemical Industries Ltd. l,l,l,5,5,5-hexafluoro-2,4-pentanedione, 4,5-bis(diphenyl-pho-sphino)-9,9-dimethylxanthene, 4,5-bis(di-ferf-butylphosphino)-9,9-dimethylx-anthene and bis[(2-diphenylphosphino)phenyl]ether were obtained from Tokyo Kasei... 

Samarium acetate tetrahydrate (5.0 g, 13 mmol) was dissolved in distilled water (60 mL) in a 100 mL flask. A solution of l,l,l,5,5,5-hexafluoro-2,4-pentanedione (10 g, 48 mmol) was added dropwise to the solution. The reaction mixture produced a precipitation of white yellow powder after stirring for 2 h at room temperature. The reaction mixture was filtered, and the resulting powder was recrystaUized from methanol to afford colorless needle crystals of the titled compound. 

Similarly, Brough et al. recorded a well-resolved spectrum of the residual protrais in a largely deuterated sample of samarium acetate. However, problems of sensitivity and background suppression were encountered, since only a few percent of residual protonated groups could be afforded to obtain reasonable spectra. 

A variety of solvents was investigated for this reaction, as shown in Table 15.1. As inferred from Table 15.1, the hydrogenolysis performance is best in more polar solvents snch as acetonitrile, acetone, ethyl acetate, and acetic acid. Only in o-dichlorobenzene is the rate of reaction ranch lower than predicted by the dielectric constant. The presence of nonpolar solvents snch as hexane and the thiol product resulted in large amonnts of the disnlfide intermediate. It has been shown that the disnlfide is the intermediate in stoichiometric rednctions such as samarium diiodide reduction of alkyl thiocyanates to thiols (11) so it is reasonable to expect it as the... 

Many of the compounds used have additional functional groups, including ester, amide, ether, and acetal. These groups may be involved in coordination to samarium and thereby influence the stereoselectivity of the reaction. 

A useful and simple method for the one-pot preparation of highly functionalized, enanhomerically pure cyclopentanes from readily accessible carbohydrate precursors has been designed by Chiara and coworkers [73]. The procedure depends on a samarium(II) iodide-promoted reductive dealkoxyhalogenahon of 6-desoxy-6-iodo-hexopyranosides such as 7-160 to produce a 6,e-unsaturated aldehyde which, after reductive cyclization, is trapped by an added electrophile to furnish the final product. In the presence of acetic anhydride, the four products 7-161 to 7-164 were obtained from 7-160. 

The acetate function of 98 was then cleaved by treatment with samarium diiodide in methanol in high yield (81 %) [44], A potential mechanism for this transformation is shown in Scheme 3.18. Reduction of the ketone function forms a samarium ketyl radical (103). Transfer of a second electron forms a carbanion (104) which undergoes p-elimination of acetate to generate the samarium enolate 105. Protonation and tautomerization then affords the observed product 107. 

Zard and coworkers have developed a synthesis of substituted dienes by reductive elimination of allylic nitroacetates (equation 33)66. Allylic nitroacetates can be prepared by condensation of nitromethane with the carbonyl compound followed by addition of formaldehyde and acetylation67. Reductive elimination can be carried out by employing either chromous acetate or samarium iodide. 

Ethyl sulfate Flammable liquids Fluorine Formamide Freon 113 Glycerol Oxidizing materials, water Ammonium nitrate, chromic acid, the halogens, hydrogen peroxide, nitric acid Isolate from everything only lead and nickel resist prolonged attack Iodine, pyridine, sulfur trioxide Aluminum, barium, lithium, samarium, NaK alloy, titanium Acetic anhydride, hypochlorites, chromium(VI) oxide, perchlorates, alkali peroxides, sodium hydride... 

Scheme 2.58 Palladium-catalyzed reduction of propargylic acetates with samarium diiodide.

Two convenient methods have been developed for the preparation of trifluoro-methyl-substituted alkoxyallenes. Reductive elimination of allylic acetates 30 with samarium diiodide leads to 31 (Scheme 8.11) [38], whereas reaction of Wittig cumu-lene 32 with phenyl trifluoromethyl ketone (33) and thermolysis of the intermediate 34 provides 35 (Scheme 8.12) [39]. 

Cerium, samarium, and other lanthanide halides promote addition of ketene silyl enol ethers to aldehydes.54 Imines react with ketene silyl acetals in the presence of Yb(03SCF3)3. Preferential addition to the imine occurs even in the presence of aldehyde... 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

A monoprotected pinacol can be obtained in 81% yield by intramolecular coupling of 2,2 -biaryldicarbaldehyde mono-dibenzyloxy acetal, using samarium(ii) iodide in THF in the presence of BF3-OEt2 (Equation (47)). As in the case of homocoupling of 2,2 -biaryldicarbaldehyde, the /ra r-isomer is produced selectively. Addition of the Lewis acid is important to obtain high yields, otherwise the yield drops to 37%. ... 

Into a solution of residue 59 (101 mg, 0.1 mmol) in 20 mL of dry toluene, kept at 60°C, was syringed, during 18 h and under argon, a freshly prepared solution of samarium diiodide in benzene-HMPA (9 1, v/v 6.3 mL, 0.51 mmol) which has been diluted with 3.8 mL of dry benzene. The solvents were distilled off under reduced pressure, and the residue was taken up in 10 mL of diethyl ether. The ether solution was washed with 10% aqueous solution of sodium bisulfite, then water, dried (MgS04), and concentrated. The crude product was dissolved in 1.5 mL of tetrahydrofuran and treated during 30 min at room temperature with 1.5 mL of a 40% aqueous solution of HF. The solution was neutralized with solid sodium carbonate, and concentrated. Flash chromatography on silica gel (cyclohexane-ethyl acetate, 3 1 to 1 2) afforded the product 80 (40.6 mg, 50%), a single isomer, as an amorphous solid. It was characterized by its diacetate [a]D +36° (c 4.0, CHClj). 

To a stirred solution of samarium diiodide (1.5 mmol) in THF (12 ml) was rapidly added a solution of a (3-hydroxy sulfone (0.5 mmol) in THF (6 ml) under an argon atmosphere. After 15 min at room temperature the reaction mixture was still blue, due to an excess of Sml2. The reaction mixture was then poured into a 10% solution of Na2S203 (20ml) and extracted with ethyl acetate. The residue was chromatographed over silica gel (hexane/ethyl acetate 99 1) to give the alkene (55-82%) as a mixture of ( )/(Z) isomers. 

Lead tetraacetate-Manganese(II) acetate, 157 Osmium tetroxide, 222 Potassium ruthenate, 259 Samarium(II) iodide, 270 reagents specific for primary alcohols Osmium tetroxide, 222 reagents specific for benzylic alcohols Cetyltrimethylammonium permanganate, 69... 

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